The present invention relates generally to power distribution systems and/or panels and, more particularly, to a power distribution system that can be configured to selectively communicate one of utility power or an uninterruptable power signal from an auxiliary power supply, such as an electric generator, to a common switch, breaker, or transfer switch breaker associated with communicating either of the utility supplied or auxiliary source supplied operating power to the load.
Many if not most buildings, regardless of use as a home, dwelling, business, or other use, are commonly powered by a primary power source such as a utility power supply. A number of electrical devices or loads, such as lights, computers, entertainment devices, pumps, fans, smoke detectors, refrigerators, equipment, etc. are fairly abundant regardless of the environment associated with the structure. Regardless of the number and/or type of load or intended use of the structure, certain loads are commonly deemed as more important or critical loads whereas others are commonly considered less important or non-critical loads. The critical loads for a home, for instance, may include the HVAC system, sump pumps, refrigerators, freezers, dishwashers, washers/dryers, and life-sustaining medical equipment. Non-critical or less important loads are commonly associated with those devices or systems that a user can tolerate extended periods of inoperability of the load in the event of an interruption to the electrical service associated with operation of the load. It is appreciated that the designation of a particular load as critical or non-critical can vary between different users and installations. As a general premise, critical loads are those loads that a particular user would prefer to be operable or powered at any given time regardless of the status of power being provided by a utility power source.
In order to ensure the availability to power to desired critical loads during a utility power or service outage, many users employ an auxiliary electrical power source. Some such supplemental power sources can include wind turbines, solar cells or collectors, battery storage, and/or engine powered generators, etc. Commonly the auxiliary power source is configured to power at least the desired critical loads associated with the particular electrical system so as to make utility power outages more tolerable, comfortable, and/or less costly due to property damage—such as caused by suspension of sump pump operations, and/or spoilage—which may be caused by extended periods of inoperability of refrigerators, freezers, and the like.
The critical and/or non-critical load designations must commonly be determined during the initial configuration of the electrical power distribution system. The non-critical loads are generally connected to non-critical branches that are hardwired to a main panel, breaker box, or main load center or simply load center. The critical loads are typically connected to critical branches that are hardwired to a separate subpanel, which is typically referred to as a transfer switch assembly or transfer panel, which can be remote or adjacent the load center but commonly include a number of switches or breakers associated with the respective loads desired to be powered by the auxiliary power source. For convenience, the transfer switch assembly or panel will hereafter be referred to as a transfer panel, with the understanding that such a designation applies to any device that is used to controls the supply of electrical power to a selected subset of electrical loads from two different power sources.
During normal primary power source operation, the loads associated with both the load center and the transfer panel are powered by the primary power source. To ensure power to the critical loads during primary power source failure, it is known to connect the transfer panel and, thus, the critical loads, to an auxiliary power source, such as an engine powered electrical generator. This connection of the transfer panel to the auxiliary power source may be done automatically when a failure or a suspension of power from the primary power source is detected. For instance, an automatic auxiliary power supply system can be configured to detect failure associated with the primary power source and configured to then automatically start operation of the auxiliary power source. Alternately, the electrical connection of the transfer panel to the auxiliary power supply can be done manually. In either instance, an electromechanical device or assembly (“transfer switch”) is used to selectively connect the circuits of the transfer panel to either the utility power source or the auxiliary power source.
A conventional auxiliary power supply system includes a power inlet box that is typically mounted on an outside wall of the building. The power inlet box interfaces, e.g., via a plug, with a generator that is typically located outside of the building. The power inlet box in turn is connected to the transfer panel that includes a transfer switch and which includes a housing that contains the power supply input selector switch, as well as a series of circuit breaker-type switches, each of which is connected in a circuit containing one or more of the critical or desired loads within the building. In the event of a power outage, the switches corresponding to these circuits are actuated to enable the circuits to be powered by the generator. Commonly, such devices include a number of interlocks that effectuate a desired switching sequence to connect the desired loads to the utility or supplemental power sources while maintaining a desired electrical isolation between the utility power source and the auxiliary power source. Particularly in manually operated transfer switch systems, the user preferably has some degree of familiarity with the switching sequence so as to maintain the desired isolation between the utility and supplemental power sources.
Thus, it is desirable to provide a distribution panel assembly that can cooperate with a main panel system and which simplifies the operations associated with supplying operating power provided from alternate power sources to a load while maintaining isolation between the alternate power sources.